WP RSS Aggregator is Disabled and Can’t Be Re-Activated

Three things I’ve noticed that are all related to my problem:

1. Most obvious: The pages with the short code (I think that’s what it’s called) show the short code and not the feed.
2. When I re-activate it, the RSS Aggregator shows up on the side menu, but when I click on it, I get “500 Internal Server Error”
3. Also, when I re-activate it and then try to click on Settings, I get “403 Forbidden”

The page I need help with: [log in to see the link]